In completed fluid and gas wells, the wellbore can be lined with piping known as tubing. The tubing can extend from the bottom of the wellbore and be opened to the earth's surface. In a naturally flowing well, formation pressure typically forces fluid and gas through the tubing, bringing it to the surface. The natural pressure in a completed well eventually diminishes, however, and when this occurs, pumping systems can be installed in the tubing to mechanically remove oil or other fluid from beneath the earth's surface.
An oil well pumping system begins with an above-ground pumping unit, which is commonly referred to as a “pumpjack,” “nodding donkey,” “horsehead pump,” “beam pump,” “sucker rod pump,” and the like. The pumping unit can create a reciprocating up and down pumping action that moves the oil or other substance being pumped out of the ground and into a flow line, from which the oil is then taken to a storage tank or other such structure.
A string of sucker rods is inserted into the tubing, which ultimately can be indirectly coupled at its north end to the above-ground pumping unit. The string of sucker rods can be coupled at its south end to a subsurface pump that is located at or near the fluid in the oil well. The subsurface pump has a number of basic components, including a barrel and a plunger. The plunger operates within the barrel, and the barrel, in turn, is positioned within the tubing. It is common for the barrel to include a standing valve and the plunger to include a traveling valve. The standing valve can have a ball therein for the purpose of regulating the passage of oil from down-hole into the pump, allowing the pumped matter to be moved northward out of the system and into the flow line, while preventing the pumped matter from dropping back southward into the hole. Oil can be permitted to pass through the standing valve and into the pump by the movement of the ball off its seat, and oil is prevented from dropping back into the hole by the seating of the ball.
South of the standing valve are a number of basic components, typically including such items as a seating nipple and a strainer or gas anchor, as well as other components. North of the standing valve, coupled to the sucker rods, can be the traveling valve. The traveling valve can regulate the passage of oil from within the pump northward in the direction of the flow line, while preventing the pumped oil from dropping back southward, in the direction of the standing valve and hole.
Oil can be pumped from a hole through a series of downstrokes and upstrokes of the pump when motion is imparted by the above-ground pumping unit. During the upstroke, formation pressure causes the ball in the standing valve to move upward, allowing the oil to pass through the standing valve and into the barrel of the oil pump. This oil can be held in place between the standing valve and the traveling valve. In the traveling valve, the ball can be located in the seated position, held there by the pressure from the oil that has been previously pumped.
On the downstroke, the ball in the traveling valve unseats, permitting the oil that has passed through the standing valve to pass therethrough. Also during the downstroke, the ball in the standing valve seats, preventing pumped oil from moving back down into the hole. The process repeats itself again and again, with oil essentially being moved in stages from the hole, to above the standing valve and in the oil pump, to above the traveling valve and out of the oil pump. As the oil pump fills, the oil passes through the pump and into the tubing. As the tubing is filled, the oil passes into the flow line, and is then taken to the storage tank or other such structure.
A number of problems can occur with fluid and gas production from wells. Fluid that is pumped from the ground typically includes solid impurities, as well as water and gas. With respect to naturally flowing wells, when relatively large volumes of water or other fluid enter the formation, the weight of this fluid can create a plug effect in the tubing, thereby slowing down or even prematurely shutting off the flow of gas to the surface. In order to continue gas flow, mechanical means, such as a pumping system, would then be required.
Furthermore, once the natural pressure in the well has depleted and a pumping system is employed to remove the subterranean fluid and gas, other problems can occur. When the pumping system is actuated, fluid and gas migrate from the wellbore to the pumping system's intake, which comprises an area of relatively lower pressure than that of the formation. Gas that enters the pumping system can cause a condition known as “gas lock,” and can slow down or even shut down production. Intake areas of pumping systems generally include nipple or strainer devices to help control the amount of gas that enters the pumping system. Often, however, gas is still allowed to enter, such that the intake of fluid is substantially reduced or even halted resulting in undesired affects.
The present application addresses these issues encountered in fluid and gas production and provides other, related, advantages.